The 12m Telescope

12M Telescope (EIE ALMA Protoype Antenna) - Kitt Peak

The Arizona Radio Observatory operates and maintains a 12 meter diameter telescope on Kitt Peak, 50 miles (80 km) WSW of Tucson, Arizona, for astronomical observations at millimeter wavelengths.

The ARO 12 Meter Telescope began as the 36 Foot Telescope, the telescope responsible for the birth of millimeter-wavelength molecular astronomy. During a period of explosive growth in this new area of astronomical research dozens of molecular species known to exist in the interstellar medium were first detected at the 36 Foot. In 1984, the telescope's reflecting surface and surface support structure were replaced and the 36 Foot was re-christened the 12 Meter. Subsequently, the scientific program has evolved from one dominated by observing programs in Astrochemistry to one with a broader mix of studies of molecular clouds and Galactic star formation, evolved stars, Astrochemistry, and external galaxies.

The 12m offers users flexibility and the opportunity to respond quickly to new scientific developments. The Observatory maintains low-noise receiving systems covering all atmospheric windows form 68 GHz to 180 GHz. Operational reliability throughout is emphasized. Flexible spectral line and continuum backends allow the observer to match the instrument to the scientific goals. The telescope control system offers great flexibility, efficiency, and convenience, and provides a proven remote observing capability.

During the period from April 2013 thru November 2014 the original 12 Meter telescope was retired and removed. It was replace by a Alma Prototype Antenna designed by ESO. The prototype was moved from it's location at the VLA to the Kitt Peak dome in late 2013 and was fully operational by November 2014.


Equipment Summary and Status - last updated July 30 2019

  • East Longitude: -111 36 53.475
  • North Latitude: +31 57 12.0
  • Elevation: 1914 meters (6280 feet)
  • Primary Reflector Diameter: 12.0 meters
  • Focal Ratio (f/D):
    • Prime Focus: 0.40
    • Secondary Focus: 8.0
  • Surface Accuracy: <60 um rms
  • Observing season: October - June
  • Carbon fiber construction
  • Altitude over Azimuth
  • Absolute pointing accuracy: 2.5” rms
  • Tracking precision: 0.2” rms
  • Efficiency: 85% +/- 5%
  • Azimuth range: +/-270°
  • Elevation range: 3° to 110°
    • Observational range: ~18° - 84°
  • Slew speed: 360° min-1
    • Observational value: 60° min-1 (Dome tracking limited)
  • Supports position-switching, beam-switching, on-the-fly mapping, and continuum observing

Front Ends

Multi - Band Receiver ( 4mm, 3mm, 2mm, 1mm, Dual polarization, SBS )

  • 3mm (ALMA Band 3; 84 – 116 GHz; Available)
    • Image Rejection: 15 dB minimum, ≥ 20 dB typical
    • Typical Tsys@90GHz = 120-160 K, Tsys@115GHz = 250-375 K
    • Best Tsys@90GHz = 85-110 K, Tsys@115GHz = 150-200 K
  • 4mm (66 – 90 GHz; Available, shared-risk)
  • 1mm (211 – 275 GHz; Available, shared-risk)
  • 2mm (In development)

Back Ends

ARO Wideband Spectrometer (AROWS)

  • Interim: two 4 GHz wide IFs (Available)
  • Final: four 4 GHz wide IFs (Unavailable)
Mode total bandwidth (MHz) Channel spacing (khz) velocity resolution at 86 GHz (km s-1) velocity resolution at 115 GHz (km s-1)
0 4000 625 4.4 3.2
1 2000 312.5 2.2 1.6
2 1000 156.25 1.1 0.8
3 500 78.125 0.54 0.40
4 250 39.0625 0.28 0.20
5 125 19.53 0.14 0.10

12 Meter MAC (2 IF Mode; Available)

  • Center frequency fixed at 6.3 GHz in receiver IF.
bandwidth (Mhz) channels usable (Mhz) usable channels △v* (khz) resolution (hkz)
800 2048 600 1536 390.6 781.2
800 4096 600 3072 195.3 390.6
400 4096 300 3072 97.6 195.3
400 8192 300 6144 48.8 97.6
200 8192 150 6144 24.4 48.8
200 16384 150 12288 12.2 24.4
100 16384 75 12288 6.1 12.2
100 32768 75 24576 3 6.1

*This is the frequency sampling interval, not the FWHM channel width.


Observing Restrictions

Sun Avoidance: The 12m requires a 10° Sun avoidance zone.

Observing: On-the-fly mapping is currently unavailable with the MAC back end.


Recently Fixed and Current Issues

MAC: Unusable for on-the-fly mapping due to hardware limitations.


For more information, please contact:
Dr. H. Alyson Ford, Manager, Radio Telescopes
alysonford@email.arizona.edu